Evaluating Rumen Fluid-Inoculated Lignocellulosic Substrates for Biogas Production
Background: The continuous decline in reserves of fossil and petroleum-based fuel and its undesirable environmental effects is a major problem faced by humanity. Biofuel production from lignocellulosic biomass such as agricultural, forest and crop residues, food waste and energy grasses is cost effective and could provide a sustainable solution to the problem. However, since a lignocellulosic substrate is recalcitrant, the choice of more effective digestion inoculums is crucial to achieve an improvement in the efficiency of digesting the substrate. Microbial community present in rumen is efficient in hydrolysis of complex organics at mesophilic temperature.
Objective: The objective of this study was to evaluate and compare biogas production potential of watercrown, potato peel, wheat and sorghum straw and sugarcane bagasse separately inoculated with rumen fluid of cow, goat and sheep.
Material and Methods: Total solid, volatile solid, C/N ratio and pH of the slurry before and after anaerobic digestion were determined following standard procedures. The volume of biogas produced was measured using water displacement method for 32 days and energy was estimated from a general methane composition of biogas and 1 m3 of methane contains 34 MJ of energy.
Results: The initial C/N ratio of slurries of potato peel ranged from 15.33 to 16.33. The highest cumulative biogas yield of 1318.83 mL g-1 VSadded-1 was obtained from potato peel inoculated with cattle rumen fluid. The cumulative biogas yield of watercrown inoculated with cattle and sheep rumen fluid was higher than that of all the slurries of sugarcane bagasse and wheat straw.
Conclusions and implications: Slurries of potato peel and watercrown grass produced the highest amount of biogas and could be used potentially for biogas production at the pilot scale.